The present invention relates to a novel device for providing high vibrational energy in the sonic or ultrasonic frequency range, i.e., greater than about 15 KHz. More specifically, the present invention is directed to the provision of an ultrasonic device for providing high intensity ultrasonic waves in the radial direction in response to the application of electric energy.
A conventional ultrasonic device which is capable of delivering ultrasonic waves convergently in the radial direction has heretofore utilized as its ring-like or circular ultrasonic radiator an electromechanical transducing element which is made of piezoelectric or electrostrictive ceramic material such as lead zirconate titanate Pb (Ti--Zr) O.sub.3 and has been employed, for example, in continuous ultrasonic mixing or emulsifying liquids as in a pipe or tube. Although the ultrasonic device of this type is known for its intense radiation of ultrasonic waves toward the center or central axis of the ring-like or circular ultrasonic radiator, it has various disadvantages in its manufacturing and in its practical use described as follows.
For one thing, a precise formation of such a ring-like or circular piezoelectric ceramic radiator is difficult in the manufacturing thereof and even more difficult is the formation of electrical insulation on the radially inner circular wall of the radiator without damaging the piezoelectric transducing property of the radiator. And further, even if the inner circular wall of the radiator of piezoelectric ceramic is well electrically insulated, there is a danger that the coated insulating layer will come off in operation due to fluid ultrasonic cavitational vibration or due to the difference of heat expansion between the coating layer and the piezoelectric ceramic radiator, thus rendering the inner wall thereof susceptible to erosion or corrosion. A still further disadvantage of the conventional ultrasonic device is a weakness of the piezoelectric ceramic radiator per se to impacts. A still further drawback is that the conventional ultrasonic device is not capable of producing a desired high power ultrasonic vibrational energy and its use is thus limited to producing a low power ultrasonic field since the size of the ring-like or circular piezoelectric ceramic ultrasonic radiator is limited by the difficulty in manufacturing.
All the above-mentioned disadvantages can be traced in their origin back to the use of a piezoelectric ceramic transducing element per se as a ring-like or circular ultrasonic radiator.
Although there have been requests from various fields of an ultrasonic application engineering such as ultrasonic chemical acceleration, ultrasonic diffusion, ultrasonic suspension, ultrasonic destruction, ultrasonic emulsion, etc., of a highly strenuous ultrasonic device of the kind which is capable of emitting an extremely high powered ultrasonic wave in the radial direction toward the center or central axis, the prior art in referring to the ultrasonic device of the above types refers to "up to 500 watts."
It is accordingly an object of the present invention to provide a novel acoustic device which is capable of radiating extremely high powered acoustic waves convergently in the radial direction.
It is another object of the present invention to provide a novel structural arrangement for an ultrasonic device wherein the ultrasonic radiator can withstand the mechanical impacts, cavitational erosion, corrosion, etc. caused in various applications such as ultrasonic acceleration of chemical reaction, suspension, destruction or diffusion of powders in a liquid, mixing or emulsifying of different liquids, and so forth.
It is a further object of the present invention to provide a novel ultrasonic device for ultrasonically treating vibration-receptive things such as fluids, fine powders and the like in a speedy and continuous manner.
These and many other objects and advantages of the present invention will become apparent from the claims and from the following detailed description when read in conjunction with the appended drawings.